INCIDENCE AND HEMODYNAMIC RESPONSE OF TRIGEMINOCARDIAC REFLEX DURING TRIGEMINAL NERVE MANIPULATION IN MICROVASCULAR DECOMPRESSION SURGERY

Abstract

The trigeminocardiac reflex (TCR) is a brainstem reflex elicited by stimulation of the trigeminal nerve, characterized by sudden bradycardia, hypotension, and occasionally asystole. Although frequently reported during skull base procedures, its incidence and detailed hemodynamic patterns during microvascular decompression (MVD) remain insufficiently quantified.

Objective

To determine the incidence, hemodynamic characteristics, and perioperative predictors of TCR during trigeminal nerve manipulation in MVD surgery.

Methods

A prospective observational study was conducted on 128 adult patients undergoing MVD for trigeminal neuralgia. Continuous intraoperative hemodynamic monitoring was performed. TCR was defined as a ≥20% decrease in heart rate and/or mean arterial pressure from baseline coinciding with trigeminal nerve manipulation. Multivariable logistic regression was used to identify independent predictors.

Results

A total of 128 patients undergoing first-time microvascular decompression for classical trigeminal neuralgia were analyzed. Intraoperative trigeminocardiac reflex (TCR) occurred in 41 patients, yielding an incidence of 32.0% (95% CI: 24.1–40.8%). TCR episodes were observed exclusively during trigeminal nerve manipulation and were reversible in all cases. Mean heart rate decreased from 72.4 ± 9.1 bpm to 47.3 ± 8.6 bpm (p < 0.001), and mean arterial pressure decreased from 86.7 ± 10.2 mmHg to 61.6 ± 9.8 mmHg (p < 0.001) during reflex episodes. Severe TCR occurred in 9.4% of patients and was associated with greater hemodynamic depression. Cisternal trigeminal nerve manipulation was the strongest independent predictor of TCR (OR 2.71, 95% CI 1.31–5.63; p = 0.007), while deeper anesthetic depth was protective (OR 0.62, 95% CI 0.39–0.97; p = 0.039).

Discussion

This study demonstrates that TCR occurs in approximately one-third of patients undergoing MVD, consistent with higher-end estimates reported in skull base literature. The magnitude of hemodynamic depression observed underscores the clinical relevance of this reflex.

Cisternal manipulation emerged as the strongest independent predictor, supporting the anatomical basis of TCR involving high-density sensory fibers near the root entry zone. The protective association of deeper anesthesia aligns with experimental data suggesting suppression of brainstem reflex arcs.

Conclusion
Trigeminocardiac reflex is a common and clinically significant intraoperative event during microvascular decompression for trigeminal neuralgia. Typically transient and reversible, its occurrence is strongly influenced by the site of trigeminal nerve manipulation and anesthetic depth. Awareness of high-risk surgical phases and optimization of anesthetic management may reduce the severity of hemodynamic disturbances